DESCRIPTION: Dental caries is the most common chronic disease of childhood, and is the biggest unmet health care need among America's children. Socioeconomic disparities in both rates of disease and treatment are a major public health issue. To date, effective biological interventions to prevent caries have not been developed. Dental plaque contains several hundred different organisms, many of which are poorly studied. A number of species have been shown to produce sufficient acid to drive pH below critical levels and to tolerate low pH. Research has primarily focused on Streptococcus mutans as the etiologic agent in caries, but based the work of previous investigators using cultivation and on our preliminary findings using molecular methods, S. mutans is not always present in caries, is often found at low levels, and additional and unexpected bacterial species may be important. In addition, comparatively little attention has been paid to identifying health-associated and potentially beneficial bacterial species that may reside in the oral cavity. For the proposed project, bacterial species present in childhood caries and health will be identified by cloning and sequencing bacterial 16S ribosomal genes amplified from DNA isolated from plaque samples. This open ended approach will allow the detection and identification of all bacterial species present, including novel, uncultivated or unexpected species. The presence and quantities of the species identified by this approach as potentially associated with caries or health will then be determined using quantitative, real-time PCR. This dual-technique approach will allow the examination of a much larger sample size than is possible by cloning and sequencing alone. Accomplishment of the proposed studies will identify the pathogens associated with the onset and progression of severe caries of the primary and young permanent dentition, and identify those bacterial species associated with a healthy dentition. This study will also provide a comprehensive catalog of the supragingival flora in children based on molecular technology. The significance of the proposed work is that identification of additional caries pathogens would provide alternative targets for biological interventions, and identification of beneficial health-associated species could provide the basis for therapeutic interventions to establish caries-resistant microbial communities.